The present invention relates to a method and apparatus for accurately controlling the inflow to and outflow from a balance tank or other intermediate storage tank of a filling machine. More particularly, the present invention relates to a method and apparatus for monitoring and controlling the inflow of a particular fluid into a balance tank of a filling machine to provide a more consistent flow of fluid from the balance tank for use in filling packages.
During the filling process of packages in the filling machine, a certain amount of product fluid is pumped out of a balance tank at various intervals to fill packages with a set amount of that fluid. In order to keep the supply of product fluid in the balance tank at a sufficient level for the continuous filling of packages, a holding tank at a dairy facility or the like is connected to the balance tank by a product line allowing fluid to be pumped to the balance tank. Accurately controlling the inflow of fluid into the balance tank of a filling machine has been the subject of various development efforts. Additionally, providing a quick and effective method for cleaning the balance tank and other apparatus for an efficient change over to a different fluid has also been the subject of development efforts.
Various methods and apparatus have been used to control and monitor the inflow rate of fluid into a balance tank in an effort to achieve equal inflow and outflow rates. For example, it is known to use a float valve at the inlet to the balance tank which is mechanically connected to a flow control valve. When the level of fluid in the tank drops below a predetermined level, the float valve opens to allow more fluid to flow in from the dairy through the product line. When sufficient fluid is in the tank, such as when the filling process is complete, the inflow of fluid raises the up to or beyond the predetermined level and the valve mechanically closes, thus preventing any additional flow of fluid into the tank from the dairy.
However, as these prior systems attempted to keep the inflow into the tank equaling the outflow from the tank, the valve was constantly open and the fluid was flowing in at a constant rate. The rate of the fluid flowing into these prior tanks could not be controlled and tended to cause foaming of the fluid in the balance tank. The foaming of the fluid is similar to how orange juice foams when it is shaken too hard. This foam in the balance tank would ultimately be pumped out of the tank and into the packages thereby causing inaccuracies in the filling process of the packages. An additional disadvantage of this prior method and apparatus was that it had to be manually cleaned.
Another prior method involved electrically connecting a valve located at the inlet to the balance tank to a two sensor probe. The probe operated by sensing a maximum fill level and a minimum fill level. When the first sensor detected that the fluid level in the tank was at the minimum level, the valve would be automatically opened to allow fluid to flow in and fill the tank. When the second sensor detected that the tank had been filled to the maximum level, the valve would be automatically closed preventing further egress of fluid into the tank. This valve system of this prior method did not provide uniform flow into the balance tank. In the position where the valve was fully open, it would allow the fluid to flow in at such a rate as to cause foaming of the fluid in the balance tank and thus inaccurate filling of the packages, as discussed above.
Additionally, the use of a two-step valve was known in the art. In one position, the valve provided for a low inflow rate of fluid into the balance tank. In the other position, the valve would be fully opened allowing for a much larger inflow rate of fluid into the balance tank. None of these prior art systems provided for a fully automatic filling system with feedback control that provided the requisite filling accuracy. Additionally, none of these systems provided for the capability of automatic cleaning of the system.